Although widely known as opium weights these bronze zoomorphic weights were used for the measurement of basic necessities throughout Burma (and also northern Thailand and Laos). A full set of weights normal consists of 10 pieces from very small sizes up the largest size known as a viss (around 1.6kg) - although some later sets had additional larger weights too.

The weights and measures system in Burma was carefully controlled and weights checked for accuracy. The production of these weights ended in Burma after the British took control of the country in 1885.

Prices vary according to scarcity of the animal/mythical beast used, with rarer designs fetching higher prices. Some of the more recent Laotian weights use particularly uncommon and collectable designs.